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21-1
Lecture 19
Circulatory System IICirculatory System II
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Capillary Network
• Capillary network made of arterial and venous capillaries
• Venules drain network• Blood flows into small
veins, medium and large veins
• Valves– Allow blood to flow
toward heart but not in opposite directionFig. 23.5
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Systemic Circulation: Veins
• Return blood from body to right atrium
• Major veins– Coronary sinus (heart)– Superior vena cava (head, neck, thorax, upper
limbs)– Inferior vena cava (abdomen, pelvis, lower
limbs)
• Types of veins– Superficial, deep, sinuses
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How Do the Three Types of Veins Differ?
• Superficial veins– Closer to the surface of the body
• Deep veins– Typically found deeper in the body and usually next to
major arteries– Typically share names with arteries (e.g. femoral vein
next to femoral artery)
• Sinuses– A modified, slightly expanded vein that lacks smooth
muscle– Incapable of changing diameter
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Veins Draining the Heart
• Cardiac veins (Great and Small)– Drain the left and right sides of the heart
• Venous blood collects in coronary sinus– Empties into right atrium
Fig. 22.9
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Venous Sinuses of the Cranium
Fig. 23.11
• Dural venous sinuses receive blood that has circulated through the brain and orbit• Blood from these sinuses empties into internal jugular vein• Internal jugular vein exits skull through the jugular foramen between temporal and occipital bones
Internal jugular vein
Dural venoussinuses
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Veins of Head and Neck
• Vertebral veins– Travel with vertebral artery through transverse foramina of
cervicals
– Drain cervicals, spinal cord, deep neck muscles
Vertebral veinExternal jugular vein
Internal jugular vein
Subclavian vein
Right brachiocephalicvein
Fig. 23.10
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Review QuestionFusion of the brachiocephalic veins will form the(a) Subclavian vein(b) Inferior vena cava(c) External jugular vein(d)Superior vena cava(e) Axillary vein
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Veins of Shoulder and Upper Limb
Fig. 23.19
• Deep veins– Radial and ulnar
veins (paired)– Brachial vein that
connects with axillary vein
• Superficial veins– Basilic vein
(becomes axillary vein)
– Cephalic vein
• Axillary vein becomes subclavian vein beneath clavicle
Superficial veinsDeep veins
Ulnar veinsRadial veins
Brachial veins
Basilic vein
Cephalic vein
Axillary vein
Subclavian vein
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Veins of Abdomen and Pelvis
Fig. 23.13
Right renal vein
Left femoral vein
Left internal iliac vein
Left external iliac vein
Left common iliac vein
Inferior vena cava
Left renal vein
Diaphragm
21-11
Hepatic Portal System
• Portal system– Begins and ends in capillaries– Heart not part of system
• Hepatic portal system– Begins with viscera of abdomen– Ends with liver
Fig. 23.16
Superior mesentericvein
Ascending colon
Duodenum
Pancreas (cut)
Hepatic portalvein
Liver
Inferior venacava
Diaphragm
Stomach
Gastric veins
Spleen
Splenic vein
Inferior mesentericvein
Small intestine
Descendingcolon
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Veins of Pelvis and Lower Limb• Deep veins
– Anterior and posterior tibial veins
– Popliteal vein– Femoral vein
• Superficial veins– Great saphenous
vein
• External iliac vein
• Internal iliac veinSuperficial veinsDeep veins
Posterior viewAnterior view
Great saphenousvein
Femoral vein
Popliteal vein
Anterior tibialveinsPosterior tibialveins
Great saphenousvein
Internal iliac vein
External iliac vein
Common iliac vein
Fig. 23.20
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Valves in Veins
-Found in medium size veins
-Allow a one-way direction of blood back to the heart
Varicose Veins-Found in superficial veins because there isn’t skeletal muscles around the vein. -Hemorroids
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Points to RememberPoints to Remember1. Three major types of veins: superficial,
deep and sinuses
2. Venous blood carried to heart by coronary sinus, superior vena cava and inferior vena cava
3. Hepatic portal system - not connected directly to heart
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Questions?